This invention relates generally to aircraft engines and more particularly to a process for providing guidance on the evaluation and disposition of diagnostic trend and fault data from such engines.
Gas turbine engines used for powering aircraft in flight are routinely subject to various maintenance procedures as part of their normal operation. To aid in the provision of such engine services, aircraft are commonly provided with onboard engine performance monitoring equipment that collects relevant trend and fault data during engine operation. Such data can be recorded onboard and accessed later by ground maintenance personnel or, alternatively, can be remotely transmitted to ground locations during flight operations. It is not uncommon for providers of engine maintenance services to operate a diagnostic center where trend data, fault data, shop records and OEM databases are integrated and used to develop optimal line maintenance strategies.
In diagnostic trend analysis, certain trend parameters, such as exhaust gas temperature, engine fuel flow, core speed, etc., that are indicative of overall engine performance and/or condition are compared to a parametric baseline for the engine. The parametric baseline is generally empirically derived or generated with an engine cycle model. Current engine trend data analysis techniques rely, in general, on visual examination of trend data to detect symptoms indicative of a need for inspection or maintenance. This approach is labor intensive, and requires considerable experience and expertise to identify real trend changes from false data. Consequently, much of the value of trending can be lost unless a user is dedicated to frequent detailed analyses of engine trend data by highly experienced personnel.
It is also known to utilize a statistical analysis technique to perform automatic detection of trend shifts by computation of a slope with a threshold to trigger an xe2x80x9calarm.xe2x80x9d Although this method of trend analysis works well, in some cases small changes may be missed or several flights may be required before the trend change can be identified. This, of course, delays detection of a potentially critical situation. In addition, this technique is not able to discern scatter and sensor drift from real engine changes. Consequently, considerable experience is still required to interpret detected symptoms. This has resulted in diminished use of trend information as a diagnostic tool.
It would be desirable, then, to have a decision making process that facilitates the evaluation and disposition of diagnostic trend and fault data while relying less on highly experienced personnel.
The above-mentioned need is met by the present invention that provides a decision making process for evaluating performance shifts identified during a diagnostic trend analysis of gas turbine engine data. The process includes first determining whether each performance shift is actionable, and then determining what maintenance action is required for actionable performance shifts. The maintenance action is determined by identifying potential causes of the actionable performance shifts and ranking the identified potential causes in most likely order.
A manual is provided for guiding a user through the decision making process. The manual includes a flow chart flow chart setting forth the steps of the decision making process and a number of tables used in the process. The tables include a false data check table having a number of questions designed to determine whether performance shifts can be attributed to a cause not related to an engine condition requiring maintenance, a persistence and magnitude table for indicating whether a performance shift""s persistence and magnitude is sufficient to consider taking action on the performance shift, a notification criteria table having a number of questions designed to determine whether the gas turbine engine data indicates that an urgent condition may exist, and traditional and historical pattern match tables that identify potential causes of performance shift.